1. Field of the Invention
This invention relates to a semiconductor switching device having a control electrode such as a thyristor or a bidirectional thyristor.
2. Description of the Prior Art
In general, thyristors refer to those of the type which comprise a semiconductor body consisting of four layers of alternately different conductivity type such as PNPN, anode and cathode electrodes contacted in a low resistance condition with at least both outer layers of the body, respectively, and a control electrode or a gate electrode for igniting the thyristor contacted with any one layer of the body, and which is switched from a non-conducting condition to a conducting condition in response to a control signal applied to the control electrode. The control electrode of such a semiconductor device is usually connected directly to an intermediate layer or an outer layer, but is often connected through a gate region formed in the outer layer and having conductivity opposite thereto. A device having the latter type of control electrode may be used in such a circuit arrangement that two thyristors connected in parallel with opposite polarities to each other are used to be operated by a single control circuit. In a semi-conductor device with such a control electrode of the type connected through a gate region formed in the anode side outer layer, such as disclosed in U.S. Pat. No. 3,284,680 to F. E. Gentry et al. (this type control electrode is hereinafter called a "remote gate"), the so-called turn-off failure by which the semiconductor device does not effect its desired operation upon transition from a conducting state to a non-conducting state is often brought about when a shorted emitter structure such as disclosed in U.S. Pat. No. 3,476,993 to R. W. Aldrich et al is taken so as to prevent the influence upon the forward breakover voltage due to the increase in temperature and/or the rate of increase in an applied forward voltage.